1. Field of the Invention
This invention pertains generally to ventilation for static structures, and more particularly to a trickle vent such as may be used in association with a window to provide requisite pressure equalization and the like. In a most preferred embodiment, the invention provides the desired ventilation while simultaneously inhibiting acoustic and thermal transmission.
2. Description of the Related Art
Shelter is considered to be a basic necessity, ranking closely in importance to food and water. While man has sought out and obtained shelter since the dawn of time, the actual embodiment of this shelter has changed over time to better fit the needs of a particular environment, and is constructed using the tools and knowledge that mankind has accumulated.
Of particular interest to the present invention is the modern building structure, particularly that which is most commonly found in industrial and commercial settings. Many commercial and industrial buildings are constructed in areas which are subjected to substantial noise and traffic. For example, a commercial building in a downtown or urban area will quite commonly be located immediately adjacent to a busy street. Similarly, industrial buildings and complexes will almost always have very noisy areas such as semi-truck or rail loading docks, manufacturing areas housing loud equipment such as punch presses, grinders, lathes and other fabricating equipment, and other very noisy areas which may be located immediately adjacent to or nearby areas requiring relative sound isolation therefrom, including offices lunch rooms and other areas. Furthermore, many industrial and commercial buildings are located immediately adjacent or very near to mass transportation, such as railways, highways, and airports. Unfortunately, mass transportation is almost universally noisy. While the present invention will be described with such structures in mind, those skilled in the art will at once recognize that there exist other buildings and windows beyond those found in industrial and commercial settings to which the present invention will apply.
In order to provide an optimum environment for those persons active within the office spaces, lunch rooms, and other such spaces, the spaces must be relatively well sound-isolated, through a broad spectrum of sounds, to prevent the external noises from interfering with activity within the generally quieter spaces. Furthermore, in some instances, such as in the case of corporate board rooms and executive offices, it may also be very desirable to not only prevent the ingress of sound, but also isolate such rooms against an egress of sound as well.
In addition to sound isolation, thermal insulation is also a concern, particularly for the exteriors of buildings. Much energy is expended maintaining proper temperature and humidity control within a building, not only for human comfort but also for the preservation of documents, equipment and the like, all of which are important to many businesses and residences.
Early sound isolation was developed hand in hand with thermal insulation. The concept of an air-tight space, provided with sufficient thermal insulation such as foam or fiberglass, was thought to address both needs of sound and thermal barriers. In fact, materials such as fiberglass and rock wool provide superior thermal insulation and also superior sound isolation. As long as the sounds and thermal energy must pass through such materials, an excellent barrier is maintained. Consequently, much design development has gone into better sealing of spaces. Advanced elastomeric seals, including both gaskets around doors and other movable barriers, and relatively more permanent seals such as are formed by various caulks, have become quite sophisticated and effective at sealing up building spaces. However, modern buildings have become so air-tight that necessary movement of air is not always provided for. As but one example, in a modern multi-story building, the passage of an elevator from floor to floor, even with a vented elevator shaft, will still lead to a displacement of air at the floors, which will in turn require equalization. Similarly, the opening or closing of a swinging door to an otherwise sealed office or room will result in significant pressure increases or decreases within the office space. Yet, to vent the office space will undesirably couple the space to adjacent, potentially much more noisy environments. Furthermore, the desired thermal insulation will be by-passed by such vents.
In recognition of a need, prior artisans have combined window room ventilators with sound dampening, and also provided a sound dampening device for cylindrical air passages. U.S. Pat. No. 1,888,711 by Bourne, which is entitled “Window ventilator and silencer” and from which the teachings are incorporated herein by reference, describes a device for installing a window to provide blower-induced ventilation into or out of a room. It also has subdivided curved air passages between the blower and the room, with sound absorbing material on the passage surfaces. U.S. Pat. No. 4,751,980 by Harry DeVane, entitled “Sound attenuation apparatus,” the teachings which are also incorporated herein by reference, describes an end-cap for a ventilation tube. The end cap consists of a mass of holes in thin plates stacked that mounts on a cylindrical airflow duct. Additional patents exemplary of the state of the art and the teachings of which are incorporated herein by reference include U.S. Pat. Nos. 977,413 by Matheson; 1,289,856 by Maxim; 1,511,920 by Tregillus; 1,655,195 by Newson; 1,922,152 by Bradbury; 4,362,223 by Meier Irmhild; 4,736,677 by Smith; 6,533,657 by Monson et al; 6,640,926 by Weinstein; and 6,648,750 by Wiseman.
Modern testing of windows comprises the generation of white noise adjacent to one surface of the window, and measuring of sound levels at various frequencies throughout the spectrum adjacent the opposite window surface, thereby identifying both a total transmission attenuation across the spectrum, and also identifying any existing resonance frequencies within the window structure that might be excited by the application of sound energy, and which will in turn couple such frequencies through the window.
While the plurality of baffles illustrated by Bourne may theoretically be designed to produce passageways that cancel broad ranges of noise, wherever a solid structure is utilized that is linked from one surface to the other, the entire structure or framework will have a particular resonant frequency which will couple sound at that frequency through from one face of a window to the other. Further, much like a bell or chime, the structure may even be induced to self-oscillate by the application of an impulse-type force, as is understood in the fields of physics and mechanical engineering. Unfortunately, window vents which rely upon an extrusion or a single solid structure may then couple sounds or even self-oscillate or ring upon application of sounds thereto. Finally, window vents of the prior art also tend not to factor in or provide for the desirable thermal insulation which is desired by most modern buildings. Consequently, the vents tend to be little more than a step backwards in time, effectively providing little more than a controlled opening through which both sound and thermal energy may pass.